13
ORIGINAL PAPER Evidence of probable paleotsunami deposits on Kho Khao Island, Phang Nga Province, Thailand Supawit Yawsangratt Witold Szczucin ´ski Niran Chaimanee Sirapapa Chatprasert Wojciech Majewski Stanislaw Lorenc Received: 3 February 2010 / Accepted: 17 January 2011 / Published online: 3 February 2011 Ó The Author(s) 2011. This article is published with open access at Springerlink.com Abstract The 2004 tsunami deposits and probable paleotsunami deposits were studied at the southern Kho Khao Island, on Andaman Sea coast of Thailand. The 2004 tsunami laid down about 8 cm of fining upward medium sand and locally about 40 cm of massive coarse sand with common mud clasts. The sediments were characterized by the presence of marine foraminiferal assemblage; however, already after 5 years many of carbonate foraminiferal tests were partly or completely dissolved. The probable paleotsunami deposits form layer about 1 m thick. It consists of massive very coarse sand with common big shells and mud clasts. Its composition suggests a marine origin and the presence of mud clasts, and similarity to the 2004 tsunami deposits suggests that the layer was left by paleotsunami, which took place probably during the late Holocene, even though two shells within the layer gave 14 C ages of 40,000 years or more. Keywords Paleotsunami deposits Indian Ocean tsunami deposits Post-depositional changes Coastal zone Thailand 1 Introduction One of the coasts severely impacted by the Indian Ocean tsunami on 26 December 2004 was the Andaman Sea coast of Thailand, where about 20,300 ha of land were flooded with seawater (UNEP 2005). The occurrence of the tsunami was unprecedented and raised a S. Yawsangratt W. Szczucin ´ski (&) S. Lorenc Institute of Geology, Adam Mickiewicz University, Mako ´w Polnych 16, 61-606 Poznan ´, Poland e-mail: [email protected] N. Chaimanee CCOP, 75/10 Rama VI Road, Phayathai, Ratchathewi, Bangkok 10400, Thailand S. Chatprasert Department of Mineral Resources, Rama VI Road, Bangkok 10400, Thailand W. Majewski Institute of Paleobiology, Polish Academy of Sciences, Twarda 51/55, 00-818 Warszawa, Poland 123 Nat Hazards (2012) 63:151–163 DOI 10.1007/s11069-011-9729-4

Evidence of probable paleotsunami deposits on Kho Khao ... · Evidence of probable paleotsunami deposits on Kho ... earthquake history, and numerical modelling. They esti- ... Kho

  • Upload
    others

  • View
    1

  • Download
    0

Embed Size (px)

Citation preview

Page 1: Evidence of probable paleotsunami deposits on Kho Khao ... · Evidence of probable paleotsunami deposits on Kho ... earthquake history, and numerical modelling. They esti- ... Kho

ORI GIN AL PA PER

Evidence of probable paleotsunami deposits on KhoKhao Island, Phang Nga Province, Thailand

Supawit Yawsangratt • Witold Szczucinski • Niran Chaimanee •

Sirapapa Chatprasert • Wojciech Majewski • Stanisław Lorenc

Received: 3 February 2010 / Accepted: 17 January 2011 / Published online: 3 February 2011� The Author(s) 2011. This article is published with open access at Springerlink.com

Abstract The 2004 tsunami deposits and probable paleotsunami deposits were studied at

the southern Kho Khao Island, on Andaman Sea coast of Thailand. The 2004 tsunami laid

down about 8 cm of fining upward medium sand and locally about 40 cm of massive

coarse sand with common mud clasts. The sediments were characterized by the presence of

marine foraminiferal assemblage; however, already after 5 years many of carbonate

foraminiferal tests were partly or completely dissolved. The probable paleotsunami

deposits form layer about 1 m thick. It consists of massive very coarse sand with common

big shells and mud clasts. Its composition suggests a marine origin and the presence of mud

clasts, and similarity to the 2004 tsunami deposits suggests that the layer was left by

paleotsunami, which took place probably during the late Holocene, even though two shells

within the layer gave 14C ages of 40,000 years or more.

Keywords Paleotsunami deposits � Indian Ocean tsunami deposits � Post-depositional

changes � Coastal zone � Thailand

1 Introduction

One of the coasts severely impacted by the Indian Ocean tsunami on 26 December 2004

was the Andaman Sea coast of Thailand, where about 20,300 ha of land were flooded with

seawater (UNEP 2005). The occurrence of the tsunami was unprecedented and raised a

S. Yawsangratt � W. Szczucinski (&) � S. LorencInstitute of Geology, Adam Mickiewicz University, Makow Polnych 16, 61-606 Poznan, Polande-mail: [email protected]

N. ChaimaneeCCOP, 75/10 Rama VI Road, Phayathai, Ratchathewi, Bangkok 10400, Thailand

S. ChatprasertDepartment of Mineral Resources, Rama VI Road, Bangkok 10400, Thailand

W. MajewskiInstitute of Paleobiology, Polish Academy of Sciences, Twarda 51/55, 00-818 Warszawa, Poland

123

Nat Hazards (2012) 63:151–163DOI 10.1007/s11069-011-9729-4

Page 2: Evidence of probable paleotsunami deposits on Kho Khao ... · Evidence of probable paleotsunami deposits on Kho ... earthquake history, and numerical modelling. They esti- ... Kho

question on tsunami hazard assessment for this coast. In principle, to provide such an

assessment it is required to have knowledge of probable tsunami sources, their likelihood

of occurrence and characteristics of tsunami from those sources at different places along

the coast. Data of earlier tsunamis present an invaluable help in quantification of these

factors. Since there are no historical accounts about any former tsunamis on the Andaman

Sea coast, it is necessary to base tsunami hazard assessment for the region on sedimentary

record of past tsunamis (paleotsunamis) and on modelling studies.

Because tsunami deposits may be represented by various sediment types, which range

from mud to boulders (e.g., Dawson and Shi 2000; Goff et al. 2001; Scheffers and Kelletat

2003; Bourgeois 2009); they may also be similar to other deposits, for instance storm

deposits (e.g., Morton et al. 2007; Switzer and Jones 2008) and may be altered by post-

depositional changes (e.g., Nichol and Kench 2008; Szczucinski 2011), in consequence

their explicit identification is often difficult. The extensive studies on 2004 onshore tsunami

deposits in the Andaman Sea coastal zone of Thailand revealed that they are incredibly

variable in regard to extent, thickness, grain size (mud to boulders), internal structures,

composition, and preservation potential. However, detail analyses allowed to discriminate

the 2004 tsunami deposits from other coastal sediments using sedimentological (e.g. Szc-

zucinski et al. 2006; Choowong et al. 2007 2008a, b; Goto et al. 2007, 2008; Hori et al.

2007; Kelletat et al. 2007; Fujino et al. 2008; Matsumoto et al. 2008), micropaleontological,

(Hawkes et al. 2007; Kokocinski et al. 2009; Sawai et al. 2009), geochemical (e.g. Szc-

zucinski et al. 2005, 2007; Kozak et al. 2008), and mineralogical (Jagodzinski et al. 2009)

characteristics. These sediment properties may serve in quest for older tsunami deposits.

Several research groups started to search for paleotsunami record on the Andaman Sea

coast of Thailand within a few months after the tsunami. However, due to similarity of

tsunami deposits to other coastal sediments, intensive post-depositional changes, lack of

lagoons or coastal lakes usually serving as good sedimentary archives, and as a result of

extensive placer mining of the coastal plain, initial quests for paleotsunami record failed

(Szczucinski et al. 2006; Tuttle et al. 2007) or faced problems during identification and age

determination of the paleotsunami events (Jankaew et al. 2008; Fujino et al. 2009; Yaw-

sangratt et al. 2009). Soon, however, compelling evidence for paleotsunamis was found on

northern part of Phra Thong Island (Fig. 1, north from Kho Khao Island). Jankaew et al.

(2008) traced several sand sheets younger than 2.5–2.8 ka. The most recent of the inferred

paleotsunamis was found to be slightly younger than AD 1300–1450. These findings were

anticipated by Fujino et al. (2009), who reported at least two sand sheets interpreted as

record of paleotsunamis, which occurred respectively more than 700 and more than

100 years ago. A bedded shell deposit interpreted as an event layer of similar age

(beginning of the fifteenth century) as the youngest sand sheet on Phra Thong Island was

reported by Harper (2005) from Krabi province (over 100 km southward). In addition,

from a region nearby Thap Lamu navy base (Fig. 1), boulders possibly deposited by a

paleotsunami of unknown age were described by Yawsangratt et al. (2009). Next to Thap

Lamu also, possible traces of mid-Holocene tsunami were found in mangrove environment

by Rhodes et al. (in review). Recently, Bruckner et al. (2010) reported likely evidence of

two paleotsunami events from Ban Bang Sak (Fig. 1), where the younger was dated to AD

1300–1400, and of older events from Pakarang Cape (Fig. 1) and located several tens of

km southward Phang Nga Bay.

Apart from the limited geological record, the tsunami recurrence period assessment for

the Andaman coast of Thailand was made by Løvholt et al. (2006) on a basis of an analysis

of the plate tectonic situation, earthquake history, and numerical modelling. They esti-

mated that it would take at least 300–400 years to accumulate the energy that was released

152 Nat Hazards (2012) 63:151–163

123

Page 3: Evidence of probable paleotsunami deposits on Kho Khao ... · Evidence of probable paleotsunami deposits on Kho ... earthquake history, and numerical modelling. They esti- ... Kho

during the December 2004 earthquake. They also estimated that tsunamis with a runup

height of 1.5–2 m and a recurrence of 50–100 years are possible; however, as discussed by

Szczucinski (2011), the sedimentary record of those smaller tsunamis would be of very low

preservation potential. Meltzner et al. (2010) found evidence for uplift of northern

Simeulue Island, near the south end of the 2004 rupture, and inferred big earthquakes in the

1390s and around 1450. One of those earthquakes likely accounts for Jankaew’s et al.

(2008) unit B, the penultimate sand sheet at Ko Phra Thong.

The objective of the present study is to extend the paleotsunami record on the

Andaman Sea coast of Thailand. It documents 2004 tsunami deposits, their post-

depositional changes and likely paleotsunami deposits found on the southern part of

Kho Khao Island. The ultimate aim of the study is to improve tsunami hazard assessment

for the studied coast.

Fig. 1 Study area. a Location of study area within Indian Ocean. In pink are marked major rupture areasduring the 2004 Sumatra–Andaman earthquake after Subarya et al. (2006). b The most severely impactedpart of Andaman Sea coast of Thailand in Phang Nga Province with marked sites with documentedpublished paleotsunami deposits (in number) and sites investigated by the authors in search forpaleotsunami. c Satellite image of Kho Khao Island with marked sites investigated by the authors forpaleotsunami

Nat Hazards (2012) 63:151–163 153

123

Page 4: Evidence of probable paleotsunami deposits on Kho Khao ... · Evidence of probable paleotsunami deposits on Kho ... earthquake history, and numerical modelling. They esti- ... Kho

2 Study site

Kho Khao Island is located in Phang Nga Province, Thailand (Fig. 1), which was heavily

affected by the 2004 tsunami. The region is in tropical climate zone with seasonal heavy

rains during southwestern monsoons. The study site is located in the coastal zone of the

southern part of the island, next to Kho Khao Island Beach Resort (Figs. 1, 2). The area is

built mainly from a series of beach ridges formed during sea level fall following the middle

Holocene sea level highstand (Sinsakul 1992). The inundation distance and maximum

runup height of the 2004 tsunami for the study site measured at the resort were 540 and

7.7 m, respectively (Szczucinski et al. 2006). The tsunami left a layer of sandy deposits

less than 0.5 m thick with variable sediment composition and structures (Jagodzinski et al.

2009, Szczucinski et al. in review).

From the west, the investigated area is bordered by beach and beach berm, which are cut

by a channel serving as stream bed and tidal channel (Fig. 2). Further landward is a low

laying, periodically flooded area (‘‘lagoon’’), which was covered by thick (40 cm on

average) 2004 tsunami deposits containing characteristic mud clasts several cm wide that

had been eroded from the mud layer below (KK6 on Fig. 3). Eastward is an elevated

terrace (about 3 m above mean sea level), covered with dense old forest. On this terrace,

most of the investigated pits were dug. Though the terrace is not continuous because it was

partly removed during old tin mining activities, the remnants of the latter are still well

visible in landscape and in characteristic deposits, which are left after separation of cas-

siterite rich fraction.

Fig. 2 Study site with marked locations of investigated pits (KK1–KK6), major landforms, andtopographical profile

154 Nat Hazards (2012) 63:151–163

123

Page 5: Evidence of probable paleotsunami deposits on Kho Khao ... · Evidence of probable paleotsunami deposits on Kho ... earthquake history, and numerical modelling. They esti- ... Kho

3 Materials and methods

In search for paleotsunami record, the authors conducted surveys in 2005, 2007, 2008, and

2009, in various sites of coastal zone in Phang Nga Province (Fig. 1; Table 1). At each of the

sites, several 1–2-m-deep pits down to groundwater table were excavated; however, apart from

documentation presented in this paper, no evidence of paleotsunami was found. Common

problem was to find the studied sequences to be disturbed by tin mining or land reclamation.

Fig. 3 Sedimentary logs and grain size distributions of the analysed samples (see Fig. 2 for pit locations)

Nat Hazards (2012) 63:151–163 155

123

Page 6: Evidence of probable paleotsunami deposits on Kho Khao ... · Evidence of probable paleotsunami deposits on Kho ... earthquake history, and numerical modelling. They esti- ... Kho

The present study is based on survey of 2004 tsunami deposits in February 2005 (KK6)

and on investigation into five pits dug in July 2009 (KK1–KK5). The sediments in excavated

pits were described, photographed, and sampled (both 2004 tsunami deposits and the older

sediments). Eighteen samples were analysed for grain size distribution through dry sieving

on a set of 13, 0.5 phi interval sieves. Ten samples (5 from 2004 tsunami deposits and 5 from

hypothetical paleotsunami deposits) were investigated for analysis of foraminiferal assem-

blages under optical microscope and SEM. The dating of two carbonate shells from hypo-

thetical paleotsunami deposits was performed by high-precision 14C measurements using

accelerator mass spectrometry (AMS) in the Poznan Radiocarbon Laboratory.

4 Results

4.1 Sediments

4.1.1 2004 tsunami deposits

In all the investigated pits, the uppermost sediments were from the 2004 tsunami. Apart

from the KK6 pit, they were relatively uniform, with thickness being on average from 8 to

Table 1 List of the sites investigated in search for paleotsunami (as marked on Fig. 1) with short infor-mation on location and dominating sediments

Site Coordinates Description

Present study, southernKho Khao Island

8�53.40N 6 pits

98�15.80E

S Phra Thong Island 9�3.80N 2 pits; multilayered sandy sediments

98�15.40E

N Kho Khao Island 9�0.20N 2 pits; multilayered sandy sediments covered with 2004 tsunamideposits, traces of land reclamation98�15.60E

Middle Kho Khao Island 8�56.20N 1 pit; massive sand with paleosoil covered by 2004 tsunamideposits98�15.70E

Thung Tuk, SE KhoKhao Island

8�53.30N 3 pits and drilling at archeological site, where a city and harbourflourished in ninth and tenth century AD; multilayered sand98�16.80E

Nearby Thung Tuk, SEKho Khao Island

8�53.90N 1 pit; brown sand on pure quartz sand below; mining area

98�16.70E

Southern Kho KhaoIsland

8�53.10N 1 pit; massive sand with paleosoil covered by 2004 tsunamideposits98�15.90E

Ban Bang Muang 8�49.90N 1 pit; multilayered sandy sediments covered with 2004 tsunamideposits98�16.10E

Ban Bang Sak 8�47.40N 4 pits; multilayered sandy sediments covered with 2004 tsunamideposits, traces of mining activity98�15.70E

Thap Lamu 8�36.10N 7 pits; massive sand with paleosoil covered by 2004 tsunamideposits and multilayered sandy sediments on mangroveremnants; traces of land reclamation; next to the bouldersdescribed by Yawsangratt et al. (2009)

98�14.70E

At each site, pits were dug down to groundwater level, usually approximately 2 m deep. In case of sites withseveral pits, the coordinates are provided for the central part of the studied area

156 Nat Hazards (2012) 63:151–163

123

Page 7: Evidence of probable paleotsunami deposits on Kho Khao ... · Evidence of probable paleotsunami deposits on Kho ... earthquake history, and numerical modelling. They esti- ... Kho

12 cm thickness (Fig. 3), although within a single pit the changes were usually in range of

1–15 cm. They were composed mostly of medium- to very coarse-grained sand, moder-

ately to poorly sorted, with grain size fining upward. The layer had a sharp uneven lower

contact with the remnants of former soil. In all the cases, development of new soil, with up

to 3-cm-thick surface organic reach layer, was observed. After 5 years, the 2004 tsunami

deposits were already disturbed by post-depositional changes, including mixing by

growing roots, rodents, and insects.

The KK6 pit (documented in 2005) was dug, in contrast to the other pits, in low-lying,

periodically flooded area (Fig. 2). The 2004 tsunami deposits were found to be 40 cm thick

and were covering black stiff mud layer with still preserved bent grass in living position

(Fig. 3). The lower 30 cm were composed of massive very coarse sand with shells and with

mud clasts in its upper part (Fig. 3). The mud clasts were of the same colour and com-

position as the underlying sediments. Their maximum diameter was about 20 cm. The

upper 10 cm of the tsunami deposits was composed of medium sand fining upward.

4.1.2 Older sediments

The deposits predating 2004 tsunami were generally composed from medium to very

coarse sand. In pits KK3 and large part of KK4, the most of the sediments consisted of

partly laminated sand capped with the remnants of pre-2004 soil. However, in case of KK1,

KK2, KK5, and the lowermost part of KK4, an approximately 1-m-thick layer of very

coarse massive sand with common big shells of nearshore snails and bivalves (with Tur-ritella spp. and Anadara spp. the most frequent) and scattered rounded, slightly elongated,

black, brownish, or yellowish mud clasts with maximum diameter in a range of 4–30 cm

was found (Fig. 3). The layer was continuous at least for 150 m. The lower contact with

underlying well sorted medium to coarse sand was sharp. The grain size was generally the

same among the sites (very coarse sand), except of the most landward site (KK2), where

also finer fractions were intercalated. At KK2 site also the number of mud clasts was the

lowest and the size the smallest. The upper part of the layer was a part of pre-2004 tsunami

soil (except of KK4); it is depleted in shells and mud clasts and was changed by the former

soil and groundwater related processes, including redox changes exemplified in changes in

colour of the sand as well as mud clasts.

4.2 Foraminifera

Foraminifera were found only in samples taken from 2004 tsunami deposits. No forami-

niferal tests were encountered in the older sediments.

In all five samples from the 2004 tsunami layers, only benthic foraminifera were present

(Table 2; Fig. 4). The assemblages are of rather low diversity and they are strongly

dominated by calcareous forms. Only two specimens of agglutinating Quinqueloculinaagglutinata were found in sample from KK1 pit. A great majority of foraminiferal test are

Table 2 The results of the AMS 14C dating

Pit Depth belowground surface (cm)

Lab no. AMS 14C age Dated material

KK1 60 Poz-33353 [43000 BP Anadara spp.

KK1 29 Poz-33354 45000 ± 4000 BP Turritella spp.

Nat Hazards (2012) 63:151–163 157

123

Page 8: Evidence of probable paleotsunami deposits on Kho Khao ... · Evidence of probable paleotsunami deposits on Kho ... earthquake history, and numerical modelling. They esti- ... Kho

poorly preserved. They bear signs of chemical and/or mechanic weathering (Fig. 4). For

this reason, it was impossible to assign between 10.6 and 62.4% of specimens into par-

ticular genus. They were placed into ‘‘unrecognized’’ category.

The most abundant (up to 56%) is Ammonia spp., greatly dominated by Ammoniaparkinsoniana and similar forms (Fig. 4. 9–11) and Pararotalia stellata (Fig. 4. 4–5).

The later, being quite robust, constitutes up to one-third of total assemblage in samples

KK1 and KK4. They are both considered to be typical for inner shelf (Hawkes et al.

2007). Less numerous are Quinqueloculina (2.6–7.2%), Amphistegina (5.5–14.3%), and

Elphidium (2.1–6.3%), the last being dominated by Elphidium crispum and Elphidiumcraticulatum. Other taxa include Eponides, Asterorotalia, and a few species of miliolid

foraminifera.

Fig. 4 SEM images of foraminifera from 2004 tsunami deposits. 1. Quinqueloculina pseudoreticulata Parr1941, KK4; 2. Quinqueloculina seminulum (Linn 1758), KK3; 3. Quinqueloculina sp. KK1; 4, 5.Pararotalia stellata (de Ferussac 1827), KK1, KK4; 6. Eponides repandus (Fitchell and Moll 1798), KK1;7. Asterorotalia pulchella (d’Orbigny 1839), KK2; 8. Ammonia tepida (Cushman 1926), KK3; 9. Ammoniaparkinsoniana (d’Orbigny 1839), KK1; 10, 11. Ammonia cf. parkinsoniana, KK1, KK2; 12, 13.Amphistegina spp., KK5, KK4; 14. Elphidium sp., KK4; 15. Elphidium craticulatum (Fitchell and Moll1798), KK2

158 Nat Hazards (2012) 63:151–163

123

Page 9: Evidence of probable paleotsunami deposits on Kho Khao ... · Evidence of probable paleotsunami deposits on Kho ... earthquake history, and numerical modelling. They esti- ... Kho

The foraminiferal assemblages seem to be modified by post-depositional processes

already 5 years after the tsunami. Samples KK4 and KK5, which show the highest per-

centages of unrecognizable foraminifera (Table 2), are devoid of minute specimens, which

is expressed in low Ammonia parkinsoniana percentages.

4.3 14C ages

Two relatively large shells (Fig. 5) of nearshore snail (Turritella spp.) and bivalve

(Anadara spp.) were collected from KK1 pit, respectively, at depth 29 and 60 cm, from a

hypothetical paleotsunami layer, and dated with AMS 14C technique. The obtained ages of

over 40 ka BP (Table 3) are very close to the border of the method application, so the dates

can be treated as minimum values only.

5 Discussion

The presented results showed that in coastal sediments of southern Kho Khao Island exist a

layer of pre-2004 tsunami sediments, which is characterized by several features typical for

A1 cm

B1 cm

Fig. 5 Samples selected for radiocarbon dating from KK 1 (a) at depth 29 cm Turritella spp. (b) at depth60 cm Anadara spp.

Table 3 Foraminiferal abundances in percentages of total assemblage in samples from 2004 tsunamideposits

Sample

KK1 KK2 KK3 KK4 KK5

Quinqueloculina spp. 7.2 3.0 7.2 3.8 2.6

Pararotalia stellata 33.9 14.0 11.6 34.4 9.5

Ammonia spp. 24.6 53.8 56.0 2.5 7.4

Amphistegina spp. 5.5 6.8 7.7 5.6 14.3

Elphidium spp. 4.2 2.7 5.8 6.3 2.1

Others 5.5 0.8 1.0 0.6 1.6

Unrecognizable 19.1 18.9 10.6 46.9 62.4

Total # of specimens 236 264 207 160 189

Nat Hazards (2012) 63:151–163 159

123

Page 10: Evidence of probable paleotsunami deposits on Kho Khao ... · Evidence of probable paleotsunami deposits on Kho ... earthquake history, and numerical modelling. They esti- ... Kho

high energy and abrupt event. Moreover, many of the characteristics are shared with 2004

tsunami deposits at the same site. Summarizing, the discussed event layer was found in pits

on the landward side of a periodically flooded area (lagoon), they have a significant

thickness (up to 1 m), they are laterally continuous (for at least 100 m), they are composed

of very coarse sand with several cm big shells (but no minor shells or foraminifera) and

they contain large mud clasts. Unfortunately it was not possible to trace the layer further

landward because of former mining.

The striking similarity with 2004 tsunami sediments found nearby (KK6), in both cases

there is a thick layer of massive very coarse sand, rich in mud clasts, suggests us to

consider a paleotsunami origin for the event layer. Storms are not frequent in the area (see

Jankaew et al. 2008 for discussion, Brand 2009). There were several tropical cyclones

recorded during the twentieth century passing next to the study area (Brand 2009).

However, despite their record can be traced in the middle continental shelf deposits

(Szczucinski 2010), they have not been registered to cause significant water level changes

on the eastern coast of Andaman Sea due to their westward oriented tracks (Brand 2009).

Moreover, the documented layer reveals several characteristics, which are suggested by

several authors to be absent in onshore storm deposits, for instance large mud clasts (see

Kortekaas and Dawson 2007; Morton et al. 2007). Mud clasts of smaller sizes have been

found on Andaman Sea coast also in 2004 tsunami deposits from other sites (e.g.

Szczucinski et al. 2006, in review; Choowong et al. 2008a). On the other hand, they have

not been found in the storm deposits forming beach ridges. Presence of shells suggests

rather marine origin of the sediments. The lack of smaller shells and foraminifera is

attributed to post-depositional dissolution. As was presented above foraminifera from 2004

tsunami deposits sampled after 5 years were already not well preserved, were partly dis-

solved and smaller foraminifera tests were probably already lost. The dissolution of car-

bonates was also well visible on the preserved bigger shells (Fig. 5).

If the discussed sediment are due to paleotsunami event then a question arise, when did

it took place. The only suitable material for dating was the shells in the sediment layer. The

obtained ages of more than 40 ka is a maximum age and it is not likely to represent the age

of the event. About 40 ka BP the sea level was approximately 80 m lower in the region

(Hanebuth and Stattegger 2004), moreover at that time the study site did not exist, since the

coastal part of Kho Khao Island is built of beach ridges formed after the mid-Holocene sea

level highstand (Sinsakul 1992). So the dated shells had to be redeposited from older

sediments and the hypothetical paleotsunami event had to take place probably in the late

Holocene, when the outer beach ridge was already formed and the lagoon already existed,

so mud could be deposited and later on eroded. The existing record of paleotsunamis from

the region reveals that about 600 years ago a tsunami took place (Harper 2005, Jankaew

et al. 2008), which left sediments in some places thicker than 2004 tsunami. The thickness

and the grain size of the tsunami deposits depend primary on the available sediment for

erosion and transport and then on the tsunami forces. However, as was found in the case of

2004 tsunami on Andaman Sea coast, there is a positive correlation between tsunami runup

height and the thickness of resultant deposits (Szczucinski et al. in review). The reported

hypothetical paleotsunami deposits are thicker than the corresponding 2004 tsunami

deposits. So, one may speculate if the event deposits documented in this paper origin from

the same paleotsunami event as described in the previous works, which could be even

larger than 2004 tsunami. Alternatively, the coastline configuration at the time of the

paleoevent could be slightly different enhancing deposition of such a thick sediment layer.

However, further extensive field and laboratory studies are necessary to confirm the age of

the event.

160 Nat Hazards (2012) 63:151–163

123

Page 11: Evidence of probable paleotsunami deposits on Kho Khao ... · Evidence of probable paleotsunami deposits on Kho ... earthquake history, and numerical modelling. They esti- ... Kho

6 Conclusions

The presented results lead to several conclusions:

1. The paleotsunami record on the Andaman Sea coasts is restricted to limited areas,

which were not subjected to placer mining and in most places is very difficult to be

recognized because of post-depositional changes and similarity to the underlying

sediments.

2. The 2004 tsunami deposits after 5 years are still visible in many places, however, are

subjected to post-depositional changes related to soil formation and dissolution of

carbonates (e.g., foraminiferal tests).

3. In the study site at southern Kho Khao, where 2004 tsunami deposits were

characterized by massive very coarse sand rich in mud clasts, similar deposits were

found in form of about 1-m-thick layer of very coarse sand rich in big marine shells

and mud clasts; its characteristics suggest that it could have been deposited by

paleotsunami event, bigger than 2004 tsunami, during the late Holocene; however,

precise dating of the event was not possible.

Acknowledgments This study was supported by the Polish Ministry of Science and Higher Educationthrough research grant No. N N523 376833 and by the Department of Mineral Resourcesin Bangkok,Thailand. Help of post-tsunami joint field teams members from Adam Mickiewicz University in Poznan,Poland, and the Department of Mineral Resources in Bangkok, Thailand, is greatly acknowledged. Inparticular, we thank R. Jagodzinski, M. Kokocinski, A. Panjasri, G. Rachlewicz, D. Saisuttichai, A. Szc-zucinska, and T. Tepsuwan for support during the field surveys and to K. Apolinarska for help in deter-mination of the dated shells taxonomy. We also thank B. Atwater and two anonymous reviewers for helpfuland detail reviews that led to substantial improvements in the paper.

Open Access This article is distributed under the terms of the Creative Commons Attribution Noncom-mercial License which permits any noncommercial use, distribution, and reproduction in any medium,provided the original author(s) and source are credited.

References

Bourgeois J (2009) Geologic effects and records of tsunamis. In: Bernard EN, Robinson AR (eds) Tsunamis.The Sea, ideas and observations on progress in the study of the seas, vol 15. Harvard University Press,Cambridge, pp 55–91

Brand S (ed) (2009) Typhoon havens handbook, Pacific. http://www.nrlmry.navy.mil/port_studies/Havens_Handbook/thh-nc/0start.htm

Bruckner H, Brill D, Jankaew K, Kelletat D, Klasen N, Vott A (2010) Tsunami deposits from the west coastof Thailand: predecessors of the 2004 Indian Ocean Tsunami—identification and dating. In: The 3rdinternational tsunami field symposium. Program and abstracts, Sendai, Japan, 10–11 April 2010,pp 53–54

Choowong M, Murakoshi N, Hisada K, Charusiri P, Daorerk V, Charoentitirat T, Chutakositkanon V,Jankaew K, Kanjanapayont P (2007) Erosion and deposition by the 2004 Indian Ocean tsunami inPhuket and Phang-nga provinces, Thailand. J Coast Res 23:1270–1276

Choowong M, Murakoshi N, Hisada K, Charoentitirat T, Charusiri P, Phantuwongraj S, Wongkok P,Choowong A, Subsayjun R, Chutakositkanon V, Jankaew K, Kanjanapayont P (2008a) Flow condi-tions of the 2004 Indian Ocean tsunami in Thailand, inferred from capping bedforms and sedimentarystructures. Terra Nova 20:141–149

Choowong M, Murakoshi N, Hisada K, Charusiri P, Charoentitirat T, Chutakositkanon V, Jankaew K,Kanjanapayont P, Phantuwongraj S (2008b) 2004 Indian Ocean tsunami inflow and outflow at Phuket,Thailand. Mar Geol 248:179–192

Dawson AG, Shi S (2000) Tsunami deposits. Pure Appl Geophys 157:875–897

Nat Hazards (2012) 63:151–163 161

123

Page 12: Evidence of probable paleotsunami deposits on Kho Khao ... · Evidence of probable paleotsunami deposits on Kho ... earthquake history, and numerical modelling. They esti- ... Kho

Fujino S, Naruse H, Suphawajruksakul A, Jarupongsakul T, Murayama M, Ichihara T (2008) Thickness andgrain-size distribution of Indian Ocean tsunami deposits at Khao Lak and Phra Thong Island, south-western Thailand. In: Shiki T, Tsuji Y, Yamazaki T, Minoura K (eds) Tsunamiites—features andimplications. Elsevier B.V., Amsterdam, Oxford, pp 123–132

Fujino S, Naruse H, Matsumoto D, Jarupongsakul T, Sphawajruksakul A, Sakakura N (2009) Stratigraphicevidence for pre-2004 tsunamis in southwestern Thailand. Mar Geol 262:25–28

Goff J, Chague-Goff C, Nichol S (2001) Paleotsunami deposits: a New Zealand perspective. Sed Geol143:1–6

Goto K, Chanavich AS, Imamura F, Kunthasap P, Matsuit T, Mioura K, Sugawara D, Yanagisawa H (2007)Distribution, origin and transport process of boulders deposited by the 2004 Indian Ocean Tsunami atPakarang Cape, Thailand. Sed Geol 202:821–827

Goto K, Imamura F, Keerthi N, Kunthasap P, Matsui T, Minoura K, Ruangrassamee A, Sugawara D,Supharatid S (2008) Distribution and significance of the 2004 Indian Ocean tsunami deposits: initialresults from Thailand and Sri Lanka. In: Shiki T, Tsuji Y, Yamazaki T, Minoura K (eds) Tsunami-ites—features and implications. Elsevier B.V., Amsterdam, Oxford, pp 105–122

Hanebuth T, Stattegger K (2004) Depositional sequences on a late Pleistocene–Holocene tropical silici-clastic shelf (Sunda Shelf, Southeast Asia). J Asian Earth Sci 23:113–126

Harper SB (2005) Bedded shell deposit at Ao Nang, Krabi province, southern Thailand; a record ofprehistoric tsunami event or extreme storm event or neither. Geol Soc America abstracts with pro-grams, Salt Lake City, UT, annual meeting, 16–19 October 2005, 37(7):75

Hawkes AD, Bird M, Cowie S, Grundy-Warr C, Horton BP, Hwai ATS, Law L, Macgregor C, Nott J, OngJE, Rigg J, Robinson R, Tan-Mullins M, Sa TT, Yasin Z, Aik LW (2007) Sediments deposited by the2004 Indian Ocean Tsunami along the Malaysia–Thailand Peninsula. Mar Geol 242:169–190

Hori K, Kuzumoto R, Hirouchi D, Umitsu M, Janjirawuttikul N, Patanakanog B (2007) Horizontal andvertical variation of 2004 Indian Ocean tsunami deposits: an example of two transects along thewestern coast of Thailand. Mar Geol 239:163–172

Jagodzinski R, Sternal B, Szczucinski W, Lorenc S (2009) Heavy minerals in 2004 tsunami deposits on KhoKhao Island, Thailand. Pol J Environ Stud 18:103–110

Jankaew K, Atwater BF, Sawai Y, Choowong M, Charoentitirat T, Martin ME, Prendergast A (2008)Medieval forewarning of the 2004 Indian Ocean tsunami in Thailand. Nature 455:1228–1231

Kelletat D, Scheffers SR, Scheffers A (2007) Field signatures of the SE-Asian mega-tsunami along the westcoast of Thailand compared to Holocene paleo-tsunami from the Atlantic region. Pure Appl Geophys164:413–431

Kokocinski M, Szczucinski W, Zgrundo A, Ibragimow A (2009) Diatom assemblages in 26 December 2004tsunami deposits from coastal zone of Thailand as provenance indicators. Pol J Environ Stud18:93–101

Kortekaas S, Dawson AG (2007) Distinguishing tsunami and storm deposits: an example from Martinhal,SW Portugal. Sed Geol 200:208–221

Kozak L, Niedzielski P, Szczucinski W (2008) The methodology and results of determination of inorganicarsenic species in mobile fractions of tsunami deposits by hyphenated technique of HPLC-HG-AAS.Int J Environ Anal Chem 88:989–1003

Løvholt F, Bungum H, Harbitz CB, Glimsdal S, Lindholm CD, Pedersen G (2006) Earthquake relatedtsunami hazard along the western coast of Thailand. Nat Hazards Earth System Sci 6:979–997

Matsumoto D, Naruse H, Fujino S, Surphawajruksakul A, Jarupongsakul T, Sakakura N, Murayama M(2008) Truncated flame structures within a deposit of the Indian Ocean tsunami: evidence of syn-sedimentary deformation. Sedimentology 55:1559–1570

Meltzner AJ, Sieh K, Chiang H-W, Shen C-C, Suwargadi BW, Natawidjaja DH, Philibosian BE, BriggsRW, Galetzka J (2010) Coral evidence for earthquake recurrence and an A.D. 1390-1455 cluster at thesouth end of the 2004 Aceh-Andaman rupture. J Geophys Res. doi:10.1029/2010JB007499 (in press)

Morton RA, Gelfenbaum G, Jaffe BE (2007) Physical criteria for distinguishing sandy tsunami and stormdeposits using modern examples. Sed Geol 200:184–207

Nichol SL, Kench PS (2008) Sedimentology and preservation potential of carbonate sand sheets depositedby the December 2004 Indian Ocean tsunami: South Baa Atoll, Maldives. Sedimentology55:1173–1187

Rhodes BP, Kirby ME, Choowong M, Jankaew K (in review) Evidence for a mid-Holocene tsunami depositalong the Andaman coast of Thailand preserved in a mangrove environment. Mar Geol

Sawai Y, Jankaew K, Martin ME, Prendergast A, Choowong M, Charoentitirat T (2009) Diatom assem-blages in tsunami deposits associated with the 2004 Indian Ocean tsunami at Phra Thong Island,Thailand. Mar Micropaleontol 73:70–79

162 Nat Hazards (2012) 63:151–163

123

Page 13: Evidence of probable paleotsunami deposits on Kho Khao ... · Evidence of probable paleotsunami deposits on Kho ... earthquake history, and numerical modelling. They esti- ... Kho

Scheffers A, Kelletat D (2003) Sedimentologic and geomorphologic tsunami imprints worldwide–a review.Earth Sci Rev 63:83–92

Sinsakul S (1992) Evidence of quarternary sea level changes in the coastal areas of Thailand: a review.J Southeast Asian Earth Sci 7:23–37

Subarya C, Chlieh M, Prawirodirdjo L, Avouac J-P, Bock Y, Sieh K, Meltzner AJ, Natawidjaja DH,McCaffrey R (2006) Plate-boundary deformation associated with the great Sumatra-Andaman earth-quake. Nature 440:46–51

Switzer AD, Jones BG (2008) Large-scale washover sedimentation in a freshwater lagoon from thesoutheast Australian coast: sea-level change, tsunami or exceptionally large storm? Holocene18:787–803

Szczucinski W (2010) Impacts of 2004 Indian Ocean tsunami on mid continental shelf of Andaman Sea. In:The 3rd international tsunami field symposium. Program and abstracts, Sendai, Japan, 10–11 April2010, pp 57–58

Szczucinski W (2011) The post-depositional changes of the onshore 2004 tsunami deposits on the AndamanSea coast of Thailand. Nat Hazards (accepted)

Szczucinski W, Niedzielski P, Rachlewicz G, Sobczynski T, Zioła A, Kowalski A, Lorenc S, Siepak J(2005) Contamination of tsunami sediments in a coastal zone inundated by the 26 December 2004tsunami in Thailand. Environ Geol 49:321–331

Szczucinski W, Chaimanee N, Niedzielski P, Rachlewicz G, Saisuttichai D, Tepsuwan T, Lorenc S, Siepak J(2006) Environmental and geological impacts of the 26 December 2004 tsunami in coastal zone ofThailand–overview of some short and long-term effects. Pol J Environ Stud 15:793–810

Szczucinski W, Niedzielski P, Kozak L, Frankowski M, Zioła A, Lorenc S (2007) Effects of rainy season onmobilization of contaminants from tsunami deposits left in a coastal zone of Thailand by the 26December 2004 tsunami. Environ Geol 53:253–264

Szczucinski W, Rachlewicz G, Chaimanee N, Saisuttichai D, Tepsuwan T, Lorenc S (in review) 26December 2004 tsunami deposits left in areas of various tsunami runup in coastal zone of Thailand.Earth, Planets Space

Tuttle M, Alam S, Atwater B, Charoentitirat T, Charusiri P, Choowong M, Fernando S, Jankaew K,Jittanoon V, Kongko W, Maxcia C, Pailoplee S, Phantuwongraj S, Rajendran K, Rhodes B, Srichan N,Tejakusuma I, Yulianto E (2007) Searching for pre-2004 tsunami deposits in Thailand. Americangeophysical union, Spring meeting 2007, abstract #T43B-04

UNEP (2005) After the tsunami. Rapid environmental assessment, p 140, http://www.unep.org/tsunami/reports/TSUNAMI_report_complete.pdf

Yawsangratt S, Szczucinski W, Chaimanee N, Jagodzinski R, Lorenc S, Chatprasert S, Saisuttichai D,Tepsuwan T (2009) Depositional effects of 2004 tsunami and hypothetical paleotsunami near ThapLamu Navy Base in Phang Nga Province, Thailand. Pol J Environ Stud 18:17–23

Nat Hazards (2012) 63:151–163 163

123